Preparation and characteristics of Mn–Ce-doped Fe-based catalysts using metallurgical dust and mud containing iron

Metallurgical solid wastes, such as metallurgical dust and mud containing iron, are formed during metallurgical sintering. They are composed of complex components and are harmful to the environment. Alongwith the current metallurgical sintering process, NO_x emission control is the top priority of pollution control in the steel industry. This paper proposes a new idea of preparing doped low-temperature catalysts using metallurgical dust and mud containing iron. Herein, the metallurgical iron-containing mud was modified by acid leaching, and the products were doped with Ce and Mn by the precipitation method to prepare a new type of catalyst. The prepared Mn–Ce-doped mud-based catalyst (Mn_0.05Ce_0.1/ADM, the ADM represents the dust and mud from acidolysis) was characterized via X-ray diffraction, nitrogen adsorption/desorption isotherm method, scanning electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption of ammonia, and temperature-programmed reduction of hydrogen. The results showed that Mn_0.05Ce_0.1/ADM achieveda NO_x removal rate of >90% within a wide temperature range from 170 ℃ to 430 ℃. Moreover, itshowed excellent SO₂ and H₂O resistance. A microstructural analysis revealed that the strong interaction between Fe–Ce–Mn could improve the surface acidity of the catalyst, thus increasing Lewis acid sites. Further, the active components of Mn_0.05Ce_0.1/ADM prepared by Ce and Mn exhibited good dispersion and an excellent mesoporous structure. In particular, Mn doping could inhibit the crystallization degree on the catalyst surface, improve the dispersed state of the active components in Mn_0.05Ce_0.1/ADM, and help improve the catalyst SCR (Selective Catalytic Reduction) activity. Combined with theanalysis of the factors influencing the catalyst, the results showed that the Ce–Mn doped catalyst increased the Fe³⁺ concentration while sacrificing a certain amount of Ce³⁺ and high-valent Mn⁺, achieving the most balanced denitration activity. Mn_0.05Ce_0.1/ADM formed more NO active centers by increasing the Lewis acid content to promote the generation of nitrate species and NO₂. Moreover, Mn doping enhanced the Fe–Ce synergy, which makes active species (Mn–Ce–Fe) easier reduction. In particular, the increase in surface oxygen mobility could significantly improve the low-temperature activity of the catalyst. The water and sulfur resistance tests of the three catalysts (Ce_0.1/ADM、Mn_0.05/ADM、Mn_0.05Ce_0.1/ADM) showed that Mn_0.05Ce_0.1/ADM benefited from the excellent water and sulfur resistance of Fe and Ce. The results showed that doping Ce into ADM inhibited the adsorption of H₂O molecules on the active component β-MnO₂ and also the reaction of SO₂ molecules with the component. The results reported herein can provide theoretical references for the high-value-added utilization of metallurgical solid wastes.